Electric motor.



No. 817,807-- PATENTED APR. 17, 1906.

' 0.13. ROTH.

ELECTRIC MOTOR.

APPLICATION FILED DEC, 27, 1904.

3 SHBETS-SHEET l PATEN TED APR. 17, 1906.

C. H. ROTH. ELECTRIC MOTOR. APPLICATION FI ED 12110.27, 1904.

3 sunnrs-snnm'z NORRIS PETERS. |NC.. LITHO., WASHINGYON, D. C.

PATENTED APR. 17, 1906.

C. H. ROTH. ELECTRIC MOTOR.

APPLICATION FILED nm.27,1904

. 3 SHEETS-SHEET 3..

j rnTn STATES PATENT @FFIGE.

CHARLES H. ROTH, OF CHICAGO, ILLINOIS, ASSIGNOR TO ROTH BROS. &

CO. OF CHICAGO, ILLINOIS, A CORPORATION OF. ILLINOIS.

ELECTRlC MOTOR.

tion. I

This invention relates-to dynamoelectric machines and has particularreference to the class of motors which are intended to be driven atvarious speeds.

This invention aims principally to produce a type of motor whichWill'operate efliciently and without sparking When the brushes are setto a-tixed position regardless of the speed or direction of rotation ofthe armature.

.t is well understood that to secure good commutation without shiftingthe brushes it is necessary that the magnetic field be kept stable asregards position. This has particu lar reference to the posit-ion ot'the neutral plane. Any shifting of the magnetism shifts the neutralplaneout of alinement with the brushes and causes sparking at thebrushes. In niotors'where the fields are weakened to produce changes inspeed this tendency to sparking increases as the magnetism of the polesis reduced below saturation, since. the magnetism under these conditionsshifts easily under the armature reaction, and accordingly shifts thecommutation-point.

' When the poles. are magnetically saturated,

shifting of the magnetism is to a large extent prevented, and apractically fixed point of commutatlen 1S preserved.

The main objects of this invention are to produce a type of motor inwhich the speed may be regulated by varying the strength of the magneticfields and at the same time maintaining a fixed point of commutationregardless of the speed or direction of rotation of the armature; toprovide an improved arrangement of field cores and field circuitswhereby the a re ate stren th of the mag- (1b C D netic field'mav bealtered, while the parts oi" such field which are nearest to the neutralplane will be maintained in a magneticallysaturated condition, andthereby prevent the shifting of the magnetic field through armaturereaction, and to provide an improved form offield-framewerkparticularlyadapted tor machines in which each pole is made up ofaplurality cl inrlivirlually-excited parts.

Specification of Letters Patent.

Application filed December 27, 1904. Serial No- 238,398.

. left-handed.

Patented April 7, 1906.

I accomplish these objects by the device shown in the accompanyingdrawings, in -which Figure 1. shows diagrammatically the Windings of abipolar motor constructed according to my invention, together with atype of ,controller tor regulating the speed of such motor. Fig. 2 is anend elevation of the magneticframe of the same motor. Fig. 3

illustrates the distribution of magnetism in the armature and. poles ofan ordinary bipolar motorwhen the same is running under no load. Fig. 4illustrates the magnetic conditions in the same motor when the same isrunning under heavy load and weakened field. Fig. 5 shows a motorconstructed according to the hereindescribed invention when runningunder full field strength and at its' slowest speed. F ig 6 illustratesthe effect of the magnetic iield of the same motor when the main coresof each of the poles are demagnetized. Fig. 7 illustrates the effect ofdemagnetizing all parts of the pole structure except thetrailing andleading parts of each pole, which are maintained in a saturatedcondition and prevent shifting of the cdnnnutationpoint. .Fig. 8 showsthe dcmagnetization of all parts of the pole structure except thetrailing ends of each pole, with the armature revolving in a right-handsed direction. Fig. 9 shows similar ,conditions when the rotation of thearmature is Fig. 10 is a diagrammatic view corresponding to Fig. 1, butshowing com pound winding on some of the cores.

In the construction shown in the drawings the magnetic frame of themotor consists of an annular yoke 11, having two groups ofradially-disposed coressecured thereto and extending inwardly therefromand having their inner ends conforming to the arc of a circle for thereception-of thev armature. In the form shown each group consists oflive cores, (indicated b the reference-numorals 1 to 10, inclusive.)Each group consists of a main core having a plurality of supplementalcores arranged at each side ol thesame, the main cores 1 and 2 beingconsiderably larger than the supplemental cores, and the combincd areasol the int rmcdiatc cores being much greater than the coinbinedareas ofthe cud cores ot'oarh group. A The yoke 1-1, as will be seen in Fig. '2,has a certain [Izlllsverso sectional area at cairll oi" the main coresand is successively increased in sectional area at each of thesuccessive cores I on each side of the mainpoles. Thus the yoke is ofgreatest transverse sectional area 5 between the poles 6 and 9 and thepoles 5 and 10, the increase in sectional area in each case beingproportionate to the magnetic flux from the corresponding cores.

to tivity with a minimum Weight of iron.

In Fig. 1 thewindings of the various cores are indicated byreferencenumerals corresponding to the same cores in.Fig. 2. Thearmature is indicated by the reference-nu- 5 meral 12. The brushes areindicated at 13 and14, and the connections between the various windingsof the cores will be clearly understood from Fig. 1

The line conductors, connecting the motor with the source of current,are indicated at L L. In the form of field-winding which is shownin thedrawings the main cores 1 and 2 are in the same clrcuit with each other.

The cores 8, 4, 3, and 7 are in a second circuit 2. The cores 5 and 6form another independent circuit, and the cores 9 and .10 still another.One end-of each of the field-circuits connects through the conductorwith the line conductor L, and the other end of each of the saidcircuits connects to its individual bar of the controller, as willbehereinafter described. The controller-arm 16 is connected with theconductor L of the line and is provided with a plurality; ofcontact-shoes for engaging thevarious bars and buttons of thecontroller.

Of the controller-bars numbered 17, 18, 19, and 20 each connects,respectively, with one of the field-circuits. The bars .21, 22, and 23connect with the armature-circuit. The right and left parts of thecontroller correspond, respectively, to the right and left hand rotationof the armature. The right and left bars 17, 18, 19, and 20 arerespectively connected together by the conductors indicated by dottedlines at their'upper ends. These conductors are so indicated to that thearm 16 is insulated from said con ductors when in' the position shown inFig. 1, in which case none of the motor-circuits are closed. The bars 21are respectively connected to the brushes '13 and 1.4 by the conductors24 and 25. The bars 22 are crossconnected. at their lower ends with thebars 21 that is,'the right-hand bar 22 is connected with the left bar 21and the'left-hand bar 22 is connected with the right-hand bar 21.- Thebar 23, which is continuous from left to right, is connected to theline. conductor L. The shoes 26 on. the arm 16, which bear on the bars22 and 23, are insulated from the arm 16, but are connected togather, sothat said shoes merely act as a con 6 5 nection beween the bars 22 and23, and when Thls arrangement provides the desired magnetic conduc- I nsuch resistance being indicated in the conindependent of the'circuit'ofthe cores 1 and v be open, and the showventionalway.

In the form shown in Fig. 10 the main cores 1 and, 2 and. the outersupplemental cores 5, 6, 9, and 10 are provided with windings connectedas shunts of the armature- 8o circuit in the same manner as in Fig. 1.The

cores 3, 4, '7, and 8 are also provlded with shunt-windings, as in Fig.1, and in addition to suchjwindlngs are provided with other windingswhich are connected in series with the armature-circuit. In Fig. 10 theshuntwindings are indicated by numeralshcorrespending to theirrespective cores. The series windings are indlcated by accentednumerals. In this case the line-conductor L .is connected with theseries coils 8, 4', 7,

and 3', the conductor 27 connecting the coil 3' with the switch-lever16.

The operation of the device shown is as follows: When the arm 16 is inthe position shown in Fig. 1, all circuits in the motor will armaturewill accordingly be at a standstill. When the arm 16 is turned to. theright in starting, all of the fieldcircuits will at first receive thefull strength of the current; but the armature-circuit will be at itsminimum through the introduction of the resistance 21. This is thecondition which is best for starting the motor, and the resistance inthe armature circuit prevents an abnormal rushof current therein. As thearm 16 is turned farther to the right resistance will be gradually cutout of the armature until the arm 16 comes into contact with the bar 21,when the armature will be receiving the full strength of the current,and

IIO

'the motor will then carry its full load at its slowest speed. As thecontroller leveris still farther moved to the right resistance isgradually introduced into the circuit of .the poles 1 and 2 until'suchcircuit is entirely open. Then through the continued move: ment of thelever '16 resistance is graduall introduced into the circuit of thepoles 8, 4,

3,- and 7, and finally the circuits of all the in- 1 2o, termediatepoles are cut out. Now only the oles 5, 6, 9, and 10 are. magneticallyexcited nder some conditions it maybe desirable ti reduce the current inthe leading poles in order to obtain an abnormally high speed and I2 5still preserve good commutation with fixed brushes. This can beaccomplished by a still further movement of the lever 16, whereuponresistance is introduced into the circuit of the poles 9 and 10. Exactlyth same con- 0 ditions arise when the lever-arm 16 is turned toward theleft. except that the armaturecircuitis then reversed, and the finalintroduction of the resistance takes place inthe poles 6 and 5, whichare in this case the lead backward shifting ofthe ppint of commutation.I

It will be seen that a large range of speed can be obtained in a motorconstructed according to my invention, as it is necessary for goodcommut-ation to have only enough field strength in the four poles 5, 6,9, and 10 to prevent the demagnetization of the fieldframe by themaximum loads to which the motor willbe subjected. These poles willtherefore be comparatively small and the range of speed willbe in aboutthe ratio of the size ofthese poles to the size of all of the polescombined. Thus if the poles 5, 5, 9, and 10represent one-tenth of theentire pole area then the range of speed of the motor would be about tento one. IVit-h the method of introducing resistance which has beenherein described almost any speed between the limits determined by thewinding of the fields and the relative sizes of the poles may beobtained by shifting the lever of the controller. The comparativemagnetic conditions which 'prevail during speed adjustments of theordinary type of motor and the hereindescribed form are graphicallyillustrated in Figs. 3 to 9, inclusive.

. In Fig. 3 is shown the magnetic condition of the field in the'vicinityof the armature of an ordinary two-pole motor when the same is runningunder full field strength without load. In this case the rotation of thearmature is unresisted, and there is accordingly no armature reaction todistort the magnetic In Fig. 4 the same'motor is shown under. load, butwith reduced field strength. The

fields are in this case magnetized below the state of saturation and thearmature reaction causes the magnetism to crowd back, the trailing partof the pole being to a considerable extent demagnetized, while theleading part or part of the pole which is in advance of the armatureapproaches a condition ofmagnetic saturation. This correspondsvirt-ually to shifting the position of the poles and causes acorresponding shifting of the com point atiio load to the position ofthe neutral point at heavy load in order to get the best results; Thisposition in actual practice is necessarily a compromise between the bestposition at no load and 'tliebest position at full load. This isespecially true in the case of elficient motors where thei'irmaturereaction is greater than in motors of'low'eificieiicy. It will also beseen that when the brushes are set to the best position for rmationofthearmature in one direction a"reversalofthe direction of rotationwoulllshift tli'cfma giiet ism to the opposite side ofthe polesai'id"re-""' sult in furious sparking at the brushes.

hen a motor constructed "according to my herein-described invention isoperated-'" under full load and at its slowest speed, the" field aboutthe armature would be represented graphically by Fig. All of the polesare saturated with magnetism, and there is a cordingly no shifting ofthe points of column tation. .The speed may now be increased by reducingthe strength of' the field. The field strength is at first "radual'lyreduced through the introduction of ings of the cores 1 and'2. Thentlie'field resistance into the'windstrength may be still further reducedby'the cutting out of the coils-1 and 2 and inti'oduc-i ing resistanceinto the circuitof the poles S, i,"

7, and 3. X0 change in the position of the commutation-points takesplace even when the field is weakest, since the trailing poles 5 and 6always remain saturated with magnetism, and their magnetism cantherefore not be shifted by the armature reaction. This'conditionremains true even after the leading poles 9 and 10 or 5 and 6,which'eyerthe case may be, have been reduced below their point ofsaturation or cut out'entirely from the cir-' cuit. It will thus beseenthat by properly changing the strength of the various'parts of the fieldthe commutation-point maybe kept constant at all speeds. With acontroller constructed as herein shown the desired results areaccomplished by merely shifting one lever. One of the other greatadvantages" of thi form of motor is its adaptability to-use' as acompound motor, givi ng the adyantage' of being able to obtain at'iyillany speed within the range of the motor" and maintain such speedpractically constant and withr'iu-t vari ation due to change ofload. "Itwill be seen that some .of the supplemental poles,p'i"efei* ably thepoles 3, 4;, Tfand 8, may be com;- pound wound (see Fig. l0) and willthen have a certain uniform effect as to's'peed variation from no'loadto full load no matter what the total field strength may be. Iirtliiscase the main poles l and 2 can beraried at will for different speeds,and the compound winding of the supplemental poles will c'i' nipcii'satefor sudden changes in the load'. l urt'heiy-tlie compound winding willall'ect only such poles which are compound wound and whlch'are a certainpercentage of the total pole structure. It will thus be possible toproduce any predetermined speed and. maintain such speed re gardless ofthe change of'load withi'n certain limits." 7

In an ordinarycompound motor the series and shunt 'coils'both act on'theentire 'polestrength, and'if the shunt-coilsiare weakened to change thespeed the series coils'have a greater eflect on the weakened field, sothat the weaker the current in the shunt-coils the nearer does the motortake'on the characteristics of a series motor, whichvaries in speedaccording to the loadit is called upon. to

carry. 7

By compounding the large central poles 1 and 2 the characteristics of aseries motor can be obtained, except that the supplemental polesin'shunt would set a predetermined limit to,the speed s By'compoundingthe poles 3, 4, 7, and 8, as

, in Fig. 10, the motor would tendto maintain a practically constantspeed regardless of chan esm the poles 1 and 2. The series Windin s onthese oles would produce a strong fiel' due to su den increase of loadand would thus neutralize the effect of armature reaction and help thepoles 5,6, 9, and 10 fixed commutation-point.

By compounding the outer poles '5, 6, 3,

and 10 the effect would be somewhat the same as in the case ofcompounding the poles 3, 4, 7, and 8, although it is preferable to havea" constant and saturated field between the outer poles for reasonsalready given.

The rinciples which are herein described bination of an armature; afield-magnet havas appl ed to a motor could also be applied to a dynamowhich is designed to be driven from sources of power in whi'chthe speedis not always constant.

It will be seen that numerous details of the construction shown'may bealtered without departin from the spirit of my'invention.

What claim asmy invention, and desire tosecure by Letters Patent, is.

1. In a device of the class described, the combination of a field-magnethaving a main pole and two supplemental poles, all of like polarity, oneof said supplemental poles be-. ing located at each side of said mainpole, the combined areas of said supplementalpoles being less than thatof the main pole; and

means for-changing the magnetic strength of said main pole withoutaffecting the strength of said supplemental poles, substantially asdescribed.

2-. In a'dynamo-electric machine the combination of an armature; a.field-magnet having a pair of magnetically-opposed groups of the load.Changes-in speed would then e controlled by varying the strength ofcores, ,eachgrou comprising L-a pair of end.

cores and a plura ity of intermediate cores all havin like poles opposedto' the' armature,. the po ar areas of said end cores beingsmall',

compared .to the combined area of :the'inter? medlatecores; and meansfor" changing the. ma netic strength ofthe intermediate" cores, wit outaffectingthatlofthe endcore's.

-3.-- In a dynamo-electric machine, the coinbination of an armature afield-magnet hav- 1 'ingapair of magnetically-opposed group of; coreseach group comprising a pair of end cores and three intermediate coresall having like poles opposed tothe armature, the polar areas of saidend cores being small compared to the combined polar area of theintermedi ate cores; windingson said machine; and a.

controller arranged to gradually reduce the magnetic strength first ofthe middle core and then of the next adjacent cores, Without affectingthat of the end cores.

4. In a dynamo-electric machine,'the com bination of an armature; afield-magnet having a pair of magnetically-opposed group of cores, eachcomprising a middle core, a pair of end cores located on o posite sidesof the middle core, and a pair 0 intermediate cores respectively andeachend core, all of said cores having located between the middle corelike poles opposed to'the armature; windings on the middle and end coresconnected as a shunt of the armature-circuit; windings ontheintermediate poles connected'ln series with the armature; and means forvarying the magnetic strength of the middle cores without afiecting thatof the end cores of each group; 1

5. In a dynamo-electric machine, the coming a pair ofmagnetically-opposed group of cores, each comprising a middle. core, apair of end cores located on o posite sides of the middle core, and apair 0 intermediate cores respectlvely located between the mlddie coreroe,

and each' end core, all of said cores having like poles opposed to thearmature; windings onall of said cores connected as a shunt of thearmature-circuit; additional windings on ber, 1904. CHARLES H. ROTH.

' Witnesses:

EUGENE A. RUMMLER,

GLEN C. STEPHENS.

